[R] Structural Equation Models(SEM)

[Ralf Finne]

Hi R-colleagues.

In the sem-package
i have a problem to introduce hidden variables.
As a simple example I take an ordinary factor analysis.
The program:

cmat=c(0.14855886, 0.05774635, 0.08003300, 0.04900990,
      0.05774635, 0.18042029, 0.11213013, 0.03752475,
            0.08003300, 0.11213013, 0.24646337, 0.03609901,
      0.04900990, 0.03752475, 0.03609901, 0.31702970)
rn=c("R","L","I","M")
cn=c("R","L","I","M")

tcv=matrix(cmat,nrow=4,ncol=4,dimnames=list(rn,cn))

model.RLIM <- specify.model()
   R  ->  f1, laddR,  NA
   L  ->  f1, laddL,  NA
   I  ->  f1, laddI,  NA
   M  ->  f1, laddM,  NA
   R <->  R,  dR,NA
   L <->  L,  dL,NA
   I <->  I,  dI,NA
   M <->  M,  dM,NA
   f1 <->  f1,  df1,NA

sem.RLIM=sem(model.RLIM,tcv,101)

The output:
Error in dimnames(x) <- dn : 
 length of 'dimnames' [2] not equal to array extent
In addition: Warning messages:
1: In sem.default(ram = ram, S = S, N = N, param.names = pars, var.names = vars,  :
  singular Hessian: model is probably underidentified.

2: In sem.default(ram = ram, S = S, N = N, param.names = pars, var.names = vars,  :
  refitting without aliased parameters.

I use R version 2.10.0 (2009-10-26) under Windows XP
sem_0.9-19  version.

Where did I make a mistake? Have anyone of  you knowledge
of any other package doing similar things like Confirmative Factor Analysis
Ralf Finne
Novia University of Applied Science
Vasa  Finland